One type of known vehicle airbag cover door includes a frame, comprising at least one wall defining a trajectory for deploying the airbag and an upper aperture extending at the end of said wall, and a lid covering at least one portion of the upper aperture and movable relatively to the frame so as to clear the upper aperture and allow deployment of the airbag along the deployment trajectory through the upper aperture, the lid being attached to the wall through an area forming a hinge. Such a cover door is generally obtained by injection molding. Thus the frame and the lid are formed from a same plastic material.
The lid is delimited by a slot by means of which the majority of its perimeter is spaced apart from the internal contour of the frame. The lid is then connected to the frame through only a few connecting points forming a hinge and allowing the opening of the lid in rotation relatively to the frame under the effect of the deployment of the airbag.
Such a device is generally intended to be attached to a plate supporting a trim element of an automobile vehicle. The plate is for example covered with a foam layer, itself covered with a skin in order to form the trim element, such as a dashboard, a door panel or other element and comprises weakened locations allowing a passage to be freed for the airbag during its deployment.
It is known how to produce a continuous hinge extending over the entire length of the lid. However, the forces required for driving the rotation of the lid relatively to the frame are significant and may perturb the deployment of the airbag.
In order to overcome this drawback and to reduce these forces, the hinge may be formed with several portions separated from each other, which facilitates opening of the cover door and increases the deployment velocity of the airbag. However, these different portions are individually more weakened than a continuous hinge of great length. The risks of breaking the hinge during the deployment of the airbag are then increased. This breakage may cause undesirable separation of the lid with respect to the frame.
In order to reduce these risks, the provision of a hinge is known, capable of extending during the rotation of the lid, as described in document EP-1 410 958 for example. Such a hinge for example has an area, the section of which is U-shaped, this U being deployed during the deployment of the airbag so as to extend the hinge.
However, even with such a possibility of elongating the hinge, it may still break. This is particularly true at the side edges of the lid, where the hinge is subject to more stresses during deployment of the airbag. Indeed, during this deployment the lid may tend to deform during its rotation until it causes a larger traction on the side portions of the hinge.